KR20040111002A - A radio telecommunications network, a station, and a method of sending packets of data - Google Patents

Abstract

PURPOSE: A method for transmitting data packets, a radio telecommunication station, and a radio telecommunication network are provided to enhance a net data processing rate by reducing the amount of retransmitting data. CONSTITUTION: A radio telecommunications network includes a first station and a second station. The first station sends packets of data having a predetermined length to the second station. The second station receives the data and sends to the first station indicators of which packets of data from the first station are accurately received. The second station measures received signal quality and sends information of received signal quality to the first station. The first station selects a different length dependent upon the information for further packets to be sent to the second station and to send the further packets.

Description

Data packet transmission method, wireless telecommunication station and wireless telecommunication network {A RADIO TELECOMMUNICATIONS NETWORK, A STATION, AND A METHOD OF SENDING PACKETS OF DATA}

The present invention relates to a wireless electronic communications network comprising a first station and a second station. The invention also relates to a method of transmitting a data packet from a first station to a second station in a wireless electronic communication network. The invention also relates to a wireless electronic communication station.

In a network for mobile electronic communications, the quality of the wireless connection depends on the wireless environment. In networks that include code division multiple access (CDMA), the quality of a wireless connection also depends on the level of network loading. This is because the power is limited and must be shared between wireless connections to the active user because the quality of the wireless connection tends to decrease as power is reduced or interference from other users increases.

Of course, the performance of the radio interface between the cell and the user depends on the quality of the radio connection. For example, in a bad wireless state, mobile voice users may notice that the received audio is distorted, and data application users may notice that throughput changes and sometimes spikes. The problem is making the air interface more robust.

One type of CDMA network is a Universal Mobile Telecommunications System (UMTS) network. The background of the UMTS network is provided, for example, in the Third Generation Partnership Project Technical Report TR21.905.

Wireless electronic communication networks, methods and wireless electronic communication stations according to the invention are now defined in the independent claims, which the reader should refer to. Preferred features are set in the dependent claims.

An example of the present invention is a wireless telecommunications network comprising a first station and a second station. The first station is operative to send a data packet of a predetermined length to the second station. The second station is operative to receive data and transmit an indicator to the first station indicating whether a data packet from the first station was correctly received. The second station also operates to measure the received signal quality and transmit information of the received signal quality to the first station. The first station is operative to select different lengths for other packets delivered to the second station and transmit the other packets, depending on the information.

Another example is the corresponding data packet transmission method.

In a preferred embodiment, a technique is provided for achieving higher net data throughput by changing the data packet length. The entire data packet must be correctly received to avoid repeated attempts in that data packet delivery. Thus, a simple and effective method of changing the radio state is provided.

Preferably, the data packet is a service data unit (SDU). The SDU length is adjusted in response to changing the radio channel quality. One preferred embodiment includes AM- RLC (Acknowledged Mode-Radio Link Control) transmission in a UMTS network, in which the RLC SDU length can be adjusted.

The present invention also provides a method of transmitting a data packet from a first station to a second station in a wireless electronic communication network. In a method example, the packet is predetermined in length. The second station receives the data and sends an indicator to the first station indicating that the data packet from the first station was correctly received. The second station measures the received signal quality and transmits the received signal quality information to the first station. The first station selects another length for another packet to be sent to the second station, depending on the information.

The present invention also provides a wireless electronic communication station operative to transmit data packets of a predetermined length. The example also operates to receive an indicator indicating that the data packet was received correctly and information regarding the quality of the received signal. The station operates according to the information, selecting another length for another packet to be transmitted and transmitting the other packet.

1 is a diagram illustrating a UMTS network and a mobile user terminal;

FIG. 2 is a diagram showing a protocol stack used in each;

3 is a diagram schematically illustrating an RLC operation in transmission;

4 is a diagram schematically illustrating an RLC operation upon reception;

5 illustrates the RLC operation in more detail;

6 is a diagram illustrating how the SDU size is adjusted to various signal quality thresholds;

7 is an example illustrating the approach.

Explanation of symbols for the main parts of the drawings

56: data packet

58, 60, 62: SDU

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings as examples.

A preferred network is the Universal Mobile Communication System (UMTS) Terrestrial Access Network (UTRAN), a type of wideband code division multiple access (W-CDMA) for mobile electronic communications. The UTRAN network is originally as shown in FIG. For clarity, only one radio network controller and two base stations of the UTRAN network 2 are shown. As shown in this figure, the UTRAN network 2 includes a base station 4. Each base station (Node B in UMTS terminology) 4 typically has three cells (not shown) because the base station 4 has three directional antennas (not shown) with an azimuth angle of 120 degrees to each other. 6) (ie radio coverage areas, also known as sectors). A radio network controller (RNC) 8, which is connected to the rest of the electronic communication "world" (not shown), controls several base stations 4 and thus multiple cells 6, respectively. The base station 4 is connected to its own controlled radio network controller (RNC) 8 via its respective interface 10, known as the IuB interface. In use, a mobile user terminal 12 (also referred to as a User Equipment (UETS) in UMTS terminology) is a wireless network controller serving through at least one cell 6 of at least one base station 4. communicate with a radio network controller (RNC) 8 (ie, with a UTRAN network 2).

Communication between the mobile user terminal 12 and the RNC 8 is accomplished using a hierarchical layered protocol series 14 (also referred to as a protocol stack) shown in FIG. The physical layer 16 receives data to be transmitted from the medium access control (MAC) layer 18. The physical layer 16 provides various transport channels to the MAC layer 18. The different types of transport channels are defined by how and what kind of characteristic data is carried on the physical layer 16. The MAC layer 18 provides a variety of logic channels for the Radio Link Control (RLC) layer 20, which are information streams dedicated to specific type information characterizing the logic channel. The RLC layer 20 receives data for transmission from the upper layer 22. The RLC layer 20 consists of a process for processing user data, known as a user plane, and a process for processing control signaling, known as a control plane. The RLC layer 20 may provide an Acknowledgment Mode (AM) data delivery service, i.

As shown in FIG. 3 and in more detail in FIG. 5, the forwarding side 24 of the radio link control (RLC) protocol layer 20 operates in admission mode (AM). The RLC layer 20 receives service data units (also known as SDUs, also known as RLC SDUs) from higher protocol layers via an AM-SAP (Acknowledged Mode-Service Access Point, not shown) (step 26). The SDU is divided into fixed length AM Data-Protocol Data Units (PDUs) by the delivery side 24 of the RLC layer 20. The SDU is divided in size larger than the length of the applicable PDU. The PDU size is configured by a higher protocol layer, such as upper layer 22, and is usually fixed. The PDU is sent to the MAC layer 18 for transmission. The SDU discard function (not shown) on the forwarding side 24 is a forwarding buffer (not shown) if the transmission of one or more component PDUs of the SDU does not succeed even after a predetermined time has elapsed or multiple retransmission attempts have been made. Is used to remove SDUs. This discarding results in initialization upon full retransmission of the SDU initiated by the higher layer 22.

At the receiving side 32 shown in FIG. 4 and more specifically in FIG. 5, the admission mode RLC layer 20 receives an input PDU from the lower protocol layer 18 (step 34). The protocol data unit (PDU) is assembled (step 36) in a receive buffer (not shown) until the entire service data unit (SDU) is received, as a result of which the successfully received SDU is sent to the upper layer 22. Is provided (step 40). The receiver, which is a radio network controller (RNC) 8 or mobile user terminal 12, sends a corresponding RLC layer (i.e., another RNC 8 and mobile user terminal 12) of the transmitter (known as a status PDU). One or more status reports confirm the successful receipt or request retransmission of the lost PDU. Thus, a status report is sent to the transmitter to indicate whether the PDU was received correctly. Based on the acknowledgment, the transmitter (mobile user terminal 12 or RNC 8) removes the PDU from the retransmission buffer if the PDU was received correctly and re-delivers the PDU if not correctly received.

These acknowledgment and optional retransmission processes take place at both the mobile user terminal 12 and the RNC 8.

If the radio link control (RLC) layer 20 operates in an admission mode, then the net data throughput at the air interface depends on the radio state. Consider a scenario where the mobile user terminal 12 faces a bad wireless condition. The probability of retransmission is high, and the probability of discarding the protocol data unit (PDU) and service data unit (SDU) is higher than in the normal radio state. If the probability of SDU destruction is high, it can be seen that the size of the RLC Service Data Unit (SDU) is a critical factor in the net data throughput. In bad radio conditions, smaller SDU sizes will reduce the probability that SDUs are incorrectly received and destroyed, thus providing greater data throughput on the air interface, especially when using AM RLC transmission.

Accordingly, radio quality measurements such as the Bit Error Rate (BER) of a physical channel or transport channel and / or the Block Error Rate (BLER) of a transport channel are provided as feedback (reference numerals in FIG. 44) to adjust the SDU size (reference numeral 46 in FIG. 5).

The SDU size used in the radio network controller (RNC) 8 is in the downlink direction (ie to the mobile user terminal), generated by the mobile user terminal 12 and transmitted to the RNC 8. Change based on BER and / or BLER measurements of quality. The SDU size used in the mobile user terminal (UE) 12 is generated by the base station (node B) 4 instead of the RNC 8 in the uplink direction transmitted to the UE 12 via the control channel ( That is, based on the BER and / or BLER measurements of the radio connection quality (from the mobile user terminal). Physical layer 16 performs BER measurements on a physical or transport channel. BLER measurement is performed on the transport channel by the medium access control (MAC) protocol layer 18.

Measurements are made frequently at the receiving side 32 (at the mobile user terminal 12 or RNC 8) and the information is often passed back to the transmitting side (at another mobile user terminal 12 or RNC 8). This allows for an appropriate and fast, ie dynamic adjustment of the SDU size.

SDU size setting (step 46) is performed by an upper protocol 22 or by an intermediate protocol layer (not shown), such as Packet Data Convergence Protocol (PDCP).

A suggested threshold for measured signal quality, in which the SDU size is changed, is shown schematically in FIG. 6. The SDU size is reduced from its maximum size 0 to size 1 if the bit error rate BER is greater than the first threshold 50. Similarly, the SDU size is reduced from size 1 to size 2 and so on if the BER is greater than the second threshold 52. In the example of the Internet protocol as upper layer 22, the SDU size is selected according to the measured BER, shown in Table 1 below.

In some embodiments, the threshold is set in view of this factor, such as the delay involved to maximize the net throughput gain.

Example scenario

7 further illustrates the proposed approach. Assume that a data packet (i.e., RLC SDU) 56 received from a higher layer is 500 bytes in size, and each data packet is divided into a series of PDUs small enough to be easily delivered on the air interface. For example, an SDU of 500 bytes is typically divided into 13 PDUs, each of which is 320 bits (8 bits per byte, with the last of the 13 PDUs containing 160 padding bits). T is a duration in which a PDU corresponding to one SDU is transmitted through the channel shown in FIG. 7.

If the channel condition is good enough, the first SDU 56 of 500 bytes (all its component PDUs and hence) is successfully delivered on the air interface. However, when the receiving end knows that the channel state is deteriorating through the measurement of the received signal quality, the upper layer 22 controls the RLC layer 20 to reduce the service data unit (SDU) size. In the example shown in FIG. 7, the 500-byte packet 56 is divided into five SDUs 58 of 100 bytes each. As shown in Figure 7, one or more of each of the component PDUs has a maximum number of attempts after a timeout period of predetermined PDU retransmission attempts (known as SDU discard timers) or until successful delivery of the PDUs. The second 100 byte SDU 60 and the fifth 100 byte SDU 62 are not received correctly at the first time since they are still received in error after being made. Thus, the second 100 byte SDU 60 and the fifth 100 byte SDU 62 are discarded. Assuming that these two 100 byte SDUs 60, 62 are received correctly on the next transmission attempt, at least 1200 bytes of data must be transmitted on the air interface in order for the receiver to correctly deliver 1000 bytes of data to the lower layer. There is. Of course, in fact, there will be any additional PDU retransmissions.

Conversely, if a prior art approach is made in which the SDU size does not change, during a second 500 bit SDU 56 transmission, if the channel condition deteriorates, the SDU 56 is considered to not be received correctly and is therefore considered at the receiving end. It is destroyed. As a result, the entire SDU 56 of 500 bytes will have to be re-delivered. Assuming that the SDU 56 is correctly received at the first retransmission, at least 1500 bytes of data need to be transmitted over the air interface in order to correctly deliver 1000 bytes of data to the upper layer and then to the receiving end. Of course, in fact, there will be any additional PDU retransmissions.

Thus, it can be seen from this comparison that by using a small data unit in a bad channel condition, it is possible to reduce the retransmitted data transmitted to obtain the information, resulting in better net data throughput. Of course, the net data throughput is one of the main parameters for measuring the Quality of Service (QoS), that is, the overall network performance.

The preferred embodiment described above relates to a Universal Mobile Communication System (UMTS) network. Another embodiment relates to other types of CDMA or W-CDMA networks.

It is possible to reduce the retransmitted data sent to obtain the information, resulting in better net data throughput.

Claims (10)

A wireless telecommunications network comprising a first station and a second station, The first station is operative to send a data packet of a predetermined length to the second station, The second station is operative to receive the data and to send an indicator to the first station indicating that a data packet from the first station was correctly received, The second station is further operative to measure the received signal quality and send information of the received signal quality to the first station, The first station is operable to transmit another packet by selecting a different length for another packet to be transmitted to the second station according to the information. Wireless telecommunications network. The method of claim 1, The first station is operative to re-deliver the data packet (s) that are marked as not received correctly. Wireless telecommunications network. The method according to claim 1 or 2, The signal quality is measured periodically and a different packet length is selected if the first station determines that a predetermined signal quality threshold has been reached. Wireless telecommunications network. The method according to any one of claims 1 to 3, If it is determined that the signal quality has distorted beyond a predetermined level, reducing the packet length. The method according to any one of claims 1 to 4, The first station is one of a base station and a mobile user terminal, and the second station is one of another base station and a mobile user terminal. Wireless telecommunications network. The method according to any one of claims 1 to 5, The received signal quality is measured at a bit error rate (BER) or block error rate (BLER). Wireless telecommunications network. The method according to any one of claims 1 to 6, Universal Mobile Telecommunication System (UMTS) wireless electronic communication network, The first station operates according to a hierarchical protocol stack that includes a radio link control (RLC) layer operating in acknowledged mode (AM), wherein the packet is an RLC service data unit (SDU). Wireless telecommunications network. The method according to any one of claims 1 to 7, The second station is further operative to send another data packet to the first station, wherein the other data packet is each of a second predetermined length, The first station is operative to receive other data and send an indicator to the second station indicating that another data packet from the second station was correctly received, The first station is operative to measure received signal quality and send information of the received signal quality to the second station, The second station is operable to select, according to the information, a length different from the second predetermined length for another packet to be transmitted to the first station. Wireless telecommunications network. A method of transmitting data packets of a predetermined length from a first station to a second station in a wireless telecommunication network, the method comprising: The second station receives the data and sends an indicator to the first station indicating that the data packet from the first station was correctly received, The second station measures the received signal quality, and transmits information of the received signal quality to the first station, The first station selects a different length for another packet to be transmitted to the second station according to the information, and transmits the other packet. How to send a data packet. Transmit data packets of each predetermined length, Receive an indicator indicating that the data packet was received correctly and information regarding the quality of the received signal, In accordance with the information, selecting a different length for another packet to be transmitted, Operative to send the other packet Wireless electronic communication station.